You are viewing this article in the AnnArbor.com archives. For the latest breaking news and updates in Ann Arbor and the surrounding area, see MLive.com/ann-arbor

Posted on Wed, Jan 18, 2012 : 9:04 a.m.

Due to public health measures, pertussis rates in Washtenaw County drop - dramatically

By Washtenaw County Public Health

Dr. Monique Reeves, Medical Director, Washtenaw County Public Health

Pertussis, also known as whooping cough, is a highly contagious respiratory disease. It's known by the symptom of uncontrollable, violent coughing that often makes it hard to breathe. After fits of many coughs, someone with pertussis often needs to take deep breaths, which result in a "whooping" sound.

Pertussis most commonly affects infants and young children and can be fatal, especially in babies less than 1 year of age.

Breaking it down by the numbers:

In 2009, which was a record year, 81 cases of whooping cough were reported here in Washtenaw County. It was — by far — the largest number of cases since 1992, with the runner-up record of 36 cases in 2003.

In 2010, pertussis was at a record high with 232 cases reported in Washtenaw County residents. Across the country several states reported an increase in cases and/or localized outbreaks of pertussis, including a state-wide epidemic in California. Why was there such a big increase in pertussis cases?

Some likely reasons include:

Decreasing immunity in teens and adults. Many have not yet gotten their Tdap vaccine booster, and more than half of this year's cases have been in teenagers and adults.

Unvaccinated children. Parents who opt out of vaccinating their children create pockets of vulnerability in the community.

Change in pertussis testing. A newer test, called a PCR, has become the dominant method of testing and most likely we are detecting more cases than we would have in the past.

Here's where it gets interesting:

1107 Tdap vaccines were adminstered by Washtenaw County Public Health Department (WCPH) in 2010. This was part of a collaborative effort between public health and local practitioners to interrupt infection transmission within the community by improving immunization coverage.

In 2010 there were 781 Tdap vaccines administed by WCPH as part of sustained effort at improving immunization coverage.

Number of pertussis cases recorded in 2011 was 26 (almost a 900 percent reduction in cases from the previous year!).

Take aways:

Vaccine-preventable diseases like pertussis are no longer a thing of the past because of declining immunization rates.

Public Health continues to play a critical role in protecting the community's health

Comments

Jamie

Tue, Jan 31, 2012 : 3:31 a.m.

(Part 2)
According to the U.S. census bureau, there were 344,791 people in the county in 2010, of which nearly 80% are over 18 years of age (4) and are therefore presumably not compelled to receive the vaccine for school. In other words, only 0.7% of the total population of susceptible adults received the vaccine (if all the Tdap vaccines were administered by the department were to adults!). Nationwide the CDC reports that less than 10% of adults have received the vaccine. I find it incredible that we are to believe that vaccinating only a tiny propotion of the population is enough to result in reduced cases (by 900%, as Dr. Reeves claims). How is it possible for that to result in any amount of &quot;herd immunity&quot;, when for most diseases it takes at least 95% of the population to be vaccinated?
1) <a href="http://pediatrics.aappublications.org/content/115/5/1422" rel='nofollow'>http://pediatrics.aappublications.org/content/115/5/1422</a>
2) <a href="http://www.co.sanmateo.ca.us/Attachments/health/pdfs/Public%20Health/cd_program/Pertussis/Health%20Advisory_Pertussis.pdf" rel='nofollow'>http://www.co.sanmateo.ca.us/Attachments/health/pdfs/Public%20Health/cd_program/Pertussis/Health%20Advisory_Pertussis.pdf</a>
3) <a href="http://vitals.msnbc.msn.com/_news/2012/01/24/10226948-calif-cuts-whooping-cough-deaths-to-zero" rel='nofollow'>http://vitals.msnbc.msn.com/_news/2012/01/24/10226948-calif-cuts-whooping-cough-deaths-to-zero</a>
4) <a href="http://quickfacts.census.gov/qfd/states/26/26161.html" rel='nofollow'>http://quickfacts.census.gov/qfd/states/26/26161.html</a>

Jamie

Tue, Jan 31, 2012 : 3:30 a.m.

(Part 1)
Upon reading this article I was struck by how many incorrect and misleading claims were made by Dr. Reeves.
Her first claim (that pertussis is most common in infants and young children) is a relatively easy mistake to make if one is not up to date with the medical literature. In actual fact, reported cases of pertussis are notoriously inaccurate because they are only a tiny percentage of the actual number of cases occuring. One study (1) estimated that there are between 800,000 to 3.3 million cases a year in adolescents and adults. This dwarfs all reported cases of pertussis in infants and children according to the CDC's Morbidity and Mortality Weekly Reports.
Dr. Reeves also makes a tenuous claim (without any evidence whatsoever) that because an extremely tiny amount of Washtenaw county residents were vaccinated with the Tdap vaccine (1,888 total) in 2010, that there were fewer cases in 2011. First, someone with Dr. Reeve's expertise ought to know that pertussis is cyclical (typically it peaks every 2-5 years). The drop in cases in 2011 could easily be (and probably is) because there was a peak in 2010. This is what is happening in California right now (3) (there was an "epidemic" of reported cases there in 2010 and cases and deaths are now down).